By James McManus

The 26-year-old forward has confessed in his latest autobiography that when he asked to leave the club back in 2010, it was an error of judgement on his part

Manchester United striker Wayne Rooney has stated that the biggest regret of his career to date was when he asked to leave the club in 2010 due to what he perceived was a lack of ambition.

Rooney has admitted that he felt frustrated at the direction that the club was taking around that time, which coupled with his own injury problems and lack of form only served to cloud his judgement over his future, something he has since seen in a different light.

"In September 2010 my ankle puts me on the sidelines. I get frustrated with myself, my game, my injury, and everything around me. I'm stuck in a cycle of bad form but I can't get out of it. And that's when I make the biggest mistake of my football career," Rooney recalls in his new autobiography currently being serialised in the Daily Mirror.

"In October, I release a statement which publicly questions my happiness at Old Trafford. Am I better off elsewhere?

"Everyone makes a fuss. There are discussions inside United to sort out the issue, people outside United chuck their opinions around, but the thing is, nobody really knows what's going on in my life.

"None of them understand where I am in my career. They don't know where my head's at.

"The only person who really knows what's going on in there is me, but even I'm not sure what I want."

After discussions with manager Sir Alex Ferguson, though, Rooney performed a dramatic U-turn and he went on to explain how the 70-year-old boss convinced him to extend his stay at Old Trafford.

"Then the manager has his say. 'Sometimes you look in a field and you see a cow and you think it's a better cow than the one you have in your own field. And it never really works that way'," he explained.

"He's saying the grass isn't always greener, and he's right.

"I like what's in my field. I'm wrong. United want the same as me: trophies, success, to be the best."